154. The old bridge had sharp approach curves at either end, one in a deep cutting, the other a heavy side cutting on a steep spur. It was decided that, while the bridge site could not be improved, a wider carriageway was necessary and the two approaches required realignment to give better curves and sight distances in keeping with modern highway design. Heavy earthworks were unavoidable and the disposal of the earth and rock presented a problem. Partly on account of this it was decided to build a large box culvert to carry the stream. The large quantity of spoil from the improved approaches could then be disposed over and above the culvert in safety. Another important aspect was that it was just possible to build a culvert of adequate size under the centre span of the existing bridge structure and work could proceed without interference to or from road traffic. As the centre line of the old bridge was on the best line, to have built a new bridge would have necessitated considerable demolition of the existing structure and half width construction of the new.
155. The culvert is 11 feet wide by 13 feet high inside and 125 ft. in length, of which the upstream 29 ft. is curved in plan to a radius of 50 ft. Loading was selected in accordance with the Ministry of Transport recommendations for highway bridges. This required the thickness of the top and bottom slabs of the culvert to be 18" increased to 22" over a central length of 70 feet. The discharge is through a retaining wall 180 feet long and 30 feet high built on the downstream side to retain the earth filling. Culvert and wall are founded on rock. The carriageway over the culvert will be 22 feet wide, as adopted for New Territories' roads, with two 5-ft. footways. The road over the culvert will be constructed to a 500 feet radius, approach bends having radii of 250 and 290 feet respectively. Curves will be transitioned, have extra widening, and carry superelevation for an average speed of 35 m.p.h.
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154. The old bridge had sharp approach curves at either end, one in a deep cutting, the other a heavy side cutting on a steep spur. It was decided that, while the bridge site could not be improved, a wider carriageway was necessary and the two approaches required realignment to give better curves and sight distances in keeping with modern highway design. Heavy earthworks were unavoidable and the disposal of the earth and rock presented a problem. Partly on account of this it was decided to build a large box culvert to carry the stream. The large quantity of spoil from the improved approaches could then be disposed over and above the culvert in safety. Another important aspect was that it was just possible to build a culvert of adequate size under the centre span of the existing bridge structure and work could proceed without interference to or from road traffic. As the centre line of the old bridge was on the best line, to have built a new bridge would have necessitated considerable demolition of the existing structure and half width construction of the new.
155. The culvert is 11 feet wide by 13 feet high inside and 125 ft. in length of which the upstream 29 ft. is curved in plan to a radius of 50 ft. Loading was selected in accordance with the Ministry of Transport recommendations for highway bridges. This required the thickness of the top and bottom slabs of the culvert to be 18" increased to 22" over a central length of 70 feet. The discharge is through a retaining wall 180 feet long and 30 feet high built on the down stream side to retain the earth filling. Culvert and wall are founded on rock. The carriageway over the culvert will be 22 feet wide as adopted for New Territories' roads with two 5-ft. footways. the road over the culvert will be constructed to a 500 feet radius, approach bends having radii of 250 and 290 feet respectively. curves will be transitioned, have extra widening and carry erelevation for an average speed of 35 m.p.h.
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